1. Field of the Invention
The present invention relates to a passive optical network system; and more particularly to a passive optical network system employing optical network units having capability for automatic shutdown upon the detection of a malfunction, and a method for the use thereof.
2. Description of Related Art
In a typically-used form of a passive optical network (PON) system with multiple optical network units (ONUs), the transmitter (TX) of each ONU is precisely controlled by an optical line termination (OLT) unit located in a central office. The precise control is frequently provided in accordance with a protocol known as time division multiplex access, or TDMA, which allocates particular time slices for each ONU to transmit. A control protocol such as TDMA is required to avoid collision between data packets that would occur if different ONUs were to transmit simultaneously in the upstream channel. However, under certain fault conditions, an ONU can fail in such a way that it inadvertently continues to transmit during TDMA time slices in which that ONU is not authorized to transmit. The errant ONU thus compromises the entire upstream data traffic to a given OLT, because the integrity of the data from the various ONUs can no longer be assured. Thus, there exists a long-felt and unmet need in the art for a system, method, or apparatus capable of detecting such malfunctions of an ONU TX, so that corrective action can be taken.